I usually switch between Poshmark and Mercari, and normally crosspost. It’s really common for someone to find something I’ve listed on poshmark and mercari, and buy it on Mercari because I’ve listed it for less.Mercari collects the money. Once the buyer gets it, they rate you, you rate them, and the money is released for you to transfer to your bank. The buyer has to rate you within 3 days, and if they don't, your money is released. They can't return except for not as described. I've sold two items and both sales went smoothly.
That 10% selling fee really is a big difference in the long run!